IGF-1 LR3
IGF-1 LR3 (Insulin-like Growth Factor-1 Long Arg3) is a radically modified, brutally potent synthetic variant of endogenous IGF-1. Engineered specifically to bypass the body's natural growth-restricting transport proteins, its anabolic effect is estimated to be up to three times stronger than native IGF-1. Extensively utilized in elite athletic and severe tissue-wasting contexts, it directly forces extreme muscle hyperplasia (the creation of new muscle cells) rather than mere hypertrophy, while radically upregulating systemic amino acid transport and glycogen synthesis.
Quick Stats
Scientific Data
Mechanism of Action
IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a modified version of natural IGF-1 with two key changes: a 13-amino-acid extension at the N-terminus and an Arg→Glu substitution at position 3. These modifications dramatically reduce binding to IGF binding proteins (IGFBPs), resulting in a 2-3× increase in biological potency and an extended half-life of ~20-30 hours (vs <15 minutes for native IGF-1).
IGF-1 LR3 activates IGF-1 receptors on muscle cells to promote protein synthesis, nitrogen retention, and glucose uptake. It also promotes satellite cell proliferation, directly supporting muscle hypertrophy. This extended activity window makes precise dosing critical — the receptor is engaged far longer than natural IGF-1.
Source: PMID: 7488657
Background & History
IGF-1 LR3 (Long-Arg3) is a recombinant human IGF-1 with two modifications: a 13-amino-acid N-terminal extension and substitution of glutamic acid with arginine at position 3. These changes reduce binding to IGF-1 binding proteins (which inactivate native IGF-1) by 1000-fold, dramatically extending the active half-life from ~10 minutes to 20-30 hours. Developed for research use, it allows prolonged direct cellular IGF-1 receptor stimulation without the binding protein "buffering" that limits native IGF-1.
Research Use Cases
- ✓Skeletal muscle hypertrophy and hyperplasia (satellite cell activation)
- ✓Post-workout anabolic signaling augmentation
- ✓Recovery from muscle injury with enhanced mTOR signaling
- ✓Research on IGF-1 receptor-mediated growth pathways
Dosing Protocol
| Typical Dose | 20-100 mcg/day |
| Frequency | 1× daily |
| Half-Life | ~20-30 hours |
| Common Vial Sizes | 1 mg |
Dosing Protocols
Starting Dose
Standard Protocol
Body-Weight Dosing Reference
Estimated doses extrapolated from the published research range of 20–100 mcg/day (referenced to 70 kg / 154 lb). These are approximations — consult a qualified healthcare provider for personalised guidance.
| Weight | Low Dose | Target Dose | High Dose |
|---|---|---|---|
| 120 lb(54 kg) | 15 mcg | 46 mcg | 77 mcg |
| 140 lb(63 kg) | 18 mcg | 54 mcg | 90 mcg |
| 160 lb(73 kg) | 21 mcg | 63 mcg | 104 mcg |
| 180 lb(82 kg) | 23 mcg | 70 mcg | 117 mcg |
| 200 lb(91 kg) | 26 mcg | 78 mcg | 130 mcg |
| 220 lb(100 kg) | 29 mcg | 86 mcg | 143 mcg |
| 250 lb(113 kg) | 32 mcg | 97 mcg | 161 mcg |
💉 For exact syringe units based on your vial concentration, use the IGF-1 LR3 Reconstitution Calculator →
Administration
Expected Timeline
Who Is It For?
Muscle Hypertrophy
HighMost potent peptide for direct muscle protein synthesis and satellite cell proliferation. Requires careful use.
Fat Loss
ModerateImproves nutrient partitioning — carbohydrates preferentially stored as muscle glycogen rather than fat.
Reconstitution Example
Safety & Considerations
Research peptide — not FDA-approved. Risk of hypoglycemia (monitor blood glucose, have fast carbs available). May promote growth of existing tumors. Do not exceed 100 mcg/day. Cycle strictly — 4 weeks on / 4 off. Do not combine with insulin.
Regulatory & Legal Status
Competitive athletes subject to anti-doping controls should not use IGF-1 LR3.
Research Chemical
US Compounding: Not eligible / not available
⚠️ This information is for educational purposes only and may not reflect the most current regulatory updates. Always verify with official FDA, WADA, and jurisdiction-specific sources before use.
Interactions & Contraindications
Hypoglycemia risk is significant — always inject post-workout with carbohydrates available. Do not use with active cancer (strong mitogenic signal). Monitor with insulin — risk of compounded hypoglycemia. Localized fat at injection site if injected in same area repeatedly.
Synergies & Common Stacks
Ipamorelin raises endogenous GH (which then creates IGF-1 in the liver); IGF-1 LR3 directly stimulates the tissue receptor. Dual-pathway IGF-1 pathway activation.
BPC-157 drives VEGF/angiogenesis at repair sites; IGF-1 LR3 provides the anabolic mTOR signal for new tissue synthesis. Full regenerative stack.
IGF-1 LR3 vs. MK-677
| Attribute | IGF-1 LR3 | MK-677 |
|---|---|---|
| Administration | Subcutaneous injection | Oral (daily) |
| Mechanism | Direct IGF-1 receptor agonist | Ghrelin receptor agonist → GH → IGF-1 |
| IGF-1 Elevation | Direct, immediate, strong | Indirect — GH stimulation cascade |
| Half-Life | 20–30 hours (LR3 modification) | 24-hour sustained oral action |
| Muscle Uptake | Direct muscle anabolic signaling | Systemic GH/IGF-1 elevation |
| WADA Status | Prohibited (S2) | Prohibited (S2) |
Verdict: IGF-1 LR3 offers direct, potent anabolic signaling at the receptor level — typically stronger for muscle hypertrophy than MK-677. However, MK-677 also provides GH itself (bone density, sleep, recovery) via the indirect GH cascade.
Dosing Quick Reference
Frequently Asked Questions
What is the difference between IGF-1 LR3 and regular IGF-1?▼
Does IGF-1 LR3 cause hypoglycemia?▼
References
- Adams GR “"IGF-1 LR3 and skeletal muscle growth".” Exercise and Sport Sciences Reviews (2002). PMID: 12150568
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